1. Field of the Invention
The present invention relates to a silver halide color photosensitive material which despites a small coating amount of silver, is highly sensitive and is capable of reducing deterioration of bright acuity.
2. Description of the Related Art
With respect to the silver halide color photo-sensitive material, further sensitivity enhancement is being urged for increasing the user benefit of color negative films. Especially in recent years, the regular use of highly sensitive films is being promoted in accordance with the penetration of compact cameras with zooming capability and lens-equipped films which enable readily and easily coping with various exposure conditions.
This film sensitivity enhancement realizes an expansion of the photographing range of photo-sensitive materials to, for example, photographing in dark rooms, fast-shutter photographing with the use of telephoto lens like sports photography, etc. Thus, the users can have tremendous benefits therefrom. Therefore, the sensitivity enhancement of films is one of everlasting themes to be tackled in this industry.
An effective method for obtaining a highly sensitive film comprises absorbing incident light as much as possible. One means therefor is increasing of a coating amount of silver. This however has disadvantages such as increasing of film cost and inviting of deterioration of desilvering characteristics at the time of development.
Another means for increasing the amount of light absorption comprises increasing the specific surface area of photo-sensitive silver halide grains. For attaining this, wide use is being made of tabular silver halide grains with enhanced aspect ratio. However, when the aspect ratio is extremely high, this causes the thickness of tabular grains to be extremely small, thereby inviting reflection of much of incident light. For example, a structure comprising a green-sensitive silver halide emulsion layer and, disposed thereunder, a red-sensitive silver halide emulsion layer would encounter such a problem that when the aspect ratio of grains of green-sensitive silver halide emulsion layer is extremely high, much of the red component of incident light is completely reflected by the green-sensitive layer and cannot arrive at the red-sensitive layer, resulting in a serious decrease of the amount of light absorption. Therefore, the method of increasing the amount of light absorption through enhancing of the aspect ratio of tabular grains has its limits.
Further other means for increasing the amount of light absorption comprises scattering light in the film. This is a method of increasing the effective light path length in the film. Silver halide grains have a high refractive index to gelatin film and accordingly are effective as a scatterer. Regular-crystal silver halide grains exhibit a high light scattering degree to tabular grains, so that mixing of tabular grains with regular-crystal silver halide grains agrees with the above object. With respect to the silver halide color photosensitive material wherein tabular grains are mixed with regular-crystal silver halide grains, reference can be made to prior art literature: Jpn. Pat. Appln. KOKAI Publication No. (hereinafter referred to as JP-A-) 11-119361 and Japanese Patents 2881315 and 2683625 (hereinafter respectively referred to Patent References 1, 2 and 3). Patent Reference 1 discloses a silver halide color photosensitive material having a photographic constituent layer containing an emulsion of tabular grains of 5 or higher aspect ratio and an emulsion of regular-crystal silver halide grains. Patent Reference 2 discloses a silver halide photosensitive material including an emulsion layer containing an emulsion of tabular grains of 1.2 or higher aspect ratio and core/shell type regular-crystal silver halide grains. Patent Reference 3 discloses a silver halide photosensitive material including an emulsion layer containing tabular grains of 5 or higher aspect ratio and 0.01 to 0.08 μm thickness and core/shell type regular-crystal silver halide grains. Although these can exert the above effects, as described later, deterioration of bright acuity and unfavorable side effects on image quality are inevitably invited thereby.